Field of the Invention
The present invention relates to a drying device that dries ink adhering to an elongated strip-shaped printing medium, a printing apparatus including the drying device, and a drying method of drying ink adhering to an elongated strip-shaped printing medium.
Description of the Background Art
In a printing apparatus conventionally known, an image is recorded on elongated strip-shaped printing paper by ejecting ink toward the printing paper while the printing paper is transported in its longitudinal direction. Some printing apparatus of this type includes a drying mechanism employing a heat roller system. The drying mechanism employing the heat roller system heats and dries ink by making printing paper contact a surface of a heated heat roller.
The conventional printing apparatus including the drying mechanism employing the heat roller system is described in Japanese Patent Application Laid-Open No. 2015-178230, for example.
The heat roller includes a heat source such as a halogen lamp arranged inside the heat roller. When a drying process is performed, a member arranged near the heat source is increased in temperature together with the heat source. Hence, according to the drying mechanism employing the heat roller system, the member near the heat source may be cooled through blowing of gas with the intention of preventing damage of this member due to excessive temperature increase. However, if the gas brought to high temperature by absorption of heat from the member diffuses in the printing apparatus, temperature inside the apparatus may be increased to cause adverse effect on a different place in the apparatus. This may be handled by providing a temperature adjusting mechanism separately for adjusting temperature in the apparatus. However, adding the temperature adjusting mechanism substantially increases manufacturing cost for the printing apparatus.
Meanwhile, a vaporized solvent component in the ink increases the humidity of the gas (a content of the solvent component in the gas) in a neighborhood of the surface of the heat roller during the drying process. Hence, for increasing drying efficiency, it is preferable that the gas in the neighborhood of the surface of the heat roller be always replaced by fresh gas. However, supplying gas at ordinary temperature to the neighborhood of the surface of the heat roller reduces the temperature of the heat roller. This may work contrarily to reduce drying efficiency.